1. Field of the Invention
This invention relates to an electromagnetically controlled fuel injection system, and more particularly to an electromagnetically controlled system for increasing the vaporization of injected fuel.
2. Description of the Prior Art
A conventional electromagnetically controlled fuel injection system includes an electromagnetically controlled fuel injection valve and a fuel injection port of the fuel injection valve positioned at an intake manifold portion of an internal combustion engine. Therefore, this results in a shortened time period wherein injected fuel is exposed to the air stream from an air cleaner to a combustion chamber in comparison with a carburetor type system having a venturi portion to which fuel is supplied. The vaporization of the injected fuel is not sufficiently promoted by the air stream and therefore is not mixed uniformly with air. Moreover, rich and lean portions exist in the fuel density distribution in the combustion chamber. Therefore, misfiring or premature detonation may be caused when ignition occurs. Moreover, fuel particles which adhere to the inner wall of the combustion chamber gather near the top of the piston in accordance with movement of the piston. As gathered fuel particles burn at the top of the piston, the piston rings are badly damaged.
Accordingly, in another conventional electromagnetically controlled fuel injection system, an air supply path is formed so as to be open around the injection port of the fuel injection valve. Air is therefore continuously supplied for increasing the vaporization of injected fuel.
However, since an adequate supply of air to urge the vaporization is constantly maintained, the ratio of air and fuel will become too lean in an idling condition in which the supply of fuel is relatively small. This means that the stability of idle engine revolution is lessened. If the supply of fuel is increased in order to obtain an optimum air-fuel ration, the number of idle engine revolutions may be increased so as to be more than is required.